I'm using Indesign CC 2015, and I've lost the colored dots on the right side of the layer list, so I can't drag items between layers any more. I've updated to the latest version, restarted etc and they are still not there. Interestingly they are there on my macbook, but not on my imac, so I'm wondering if I have accidentally changed a setting without realizing it. Can anyone advise on how to get these 'dots' back? It's driving me crazy having to copy and paste all the time.

This is the second report I've seen where replacing prefs didn't seem to work. Do they show in a new Mac user account? If you start the Mac with the Shift Key down?

If they work in a new account, you many need replace the entire InDesign preference folders from the original account with those from the new account. If they work in a Safe Mode startup you have a software conflict, and I would suspect things like security software such as WebRoot, or plugins in the Chrome Browser.